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Step by step
How to build a raised garden bed
A raised bed warms up earlier in spring, drains well and saves your back. This guide shows how to size, build and fill a simple wooden bed that lasts for years.
1. Choose the size and place
Keep the bed no wider than about 1.2 m (4 ft), so you can reach the middle from both sides without stepping on the soil; against a wall, keep it to about 60–75 cm. Length is up to you. A height of 20–30 cm is enough for most vegetables; 60–80 cm makes gardening easier for people who cannot bend. Choose a spot with at least six hours of sun and leave paths about 45–60 cm wide between beds.
2. Pick safe, durable materials
Naturally durable wood such as larch, cedar or oak, or modern pressure-treated timber, lasts many years. Avoid old railway sleepers and wood treated with creosote or other older preservatives, which can leach into the soil. Untreated pine is cheap but may rot within a few years; a plastic liner on the inside of the boards extends its life. Use galvanized or stainless screws.
3. Build the frame
Cut the boards to length and screw them to square corner posts (about 5 × 5 cm) on the inside. On long beds, add a post or cross brace in the middle every 1.2–1.8 m so the sides do not bow out under the weight of wet soil. Check that the frame is square by measuring the diagonals.
4. Prepare the ground
Set the frame level, digging the high side in rather than packing the low side. Loosen the soil underneath with a fork so roots and water can go deeper. If weeds are a problem, lay cardboard on the bottom; it rots away within a season. Add wire mesh if moles or voles are common.
5. Fill with soil
Fill with a mix of good topsoil and compost, for example about two parts soil to one part compost, rather than bagged potting compost alone. Fill to the top: the soil settles by several centimeters in the first season. To work out the volume, multiply length × width × depth; a 2.4 × 1.2 m bed 30 cm deep needs about 0.86 m³ of soil. The Gravel calculator gives the volume for any size.
6. Plant and look after it
Add a layer of compost each year to replace what settles and feeds the plants. Raised beds dry out faster than ground beds, so water more often in summer and mulch the surface. For growing tips, see our sister site PlantWhy: How to compost at home: a beginner's guide and Starting seeds indoors: from seed tray to garden.
Common mistakes
- Building the bed too wide to reach the middle.
- Using old sleepers or creosote-treated wood.
- No middle brace on a long bed, so the sides bow out.
- Filling with garden soil only, which compacts.
- Not leaving room for settling, or not topping up each year.
Frequently asked questions
How deep should a raised bed be?
20–30 cm is enough for most vegetables; deeper beds suit root crops and poor ground underneath.
How wide should a raised bed be?
About 1.2 m if you can reach from both sides, 60–75 cm against a wall or fence.
What wood is safe for a raised bed?
Naturally durable wood such as larch or cedar, or modern pressure-treated timber. Avoid creosote-treated railway sleepers.
How much soil do I need?
Length × width × depth. A 2.4 × 1.2 m bed 30 cm deep needs about 0.86 m³.
Should I line the bottom?
Cardboard suppresses weeds; wire mesh keeps out burrowing animals. Avoid plastic on the bottom, which stops drainage.